1. Field of the Invention
The present invention relates to networking technology. More specifically, the invention relates to methods and apparatuses for providing load information.
2. Description of the Related Art
An enhancement to the Internet protocol is described in “Definition of the Differentiated Services Field (DS Field) in the IPv4 and Ipv6 Header” by Nichols et al., Request for Comments 2474, “The Internet Engineering Task Force of the Internet Society,” 1998. The entire content of this document is incorporated herein by reference for all purposes. Differentiated services, as the name implies, is a mechanism for providing different types of services to different data flows. For example, one flow may be assigned a larger bandwidth than another flow.
Within the proposed differentiated services scheme there are two types of mechanisms for forwarding packets. The first type is referred to as expedited forwarding (EF). The service emulated by EF is analogous to having a leased line. The second type of forwarding is referred to as assured forwarding (AF). AF includes several relative levels of service.
Each flow is classified into one of several AF classes. For example, the AF classes might include a gold, silver, and bronze class. Each AF class may also be associated with several loss probability levels. Each AF class and loss probability level is forwarded in a different way. For example, flows for the gold class may have a larger bandwidth than flows for the silver class.
Since it is impractical to classify packets at every router along the packet's transmission path (e.g., which path typically includes edge routers and core routers), classification is done by the edge routers. The edge routers typically handle less traffic than the core routers. The edge routers classify incoming packets into one of several predefined classes. In other words, each packet is assigned to one behavior aggregate.
After a packet is classified by an edge router and then routed to a core router, the receiving core routers then merely have to identify the packet as belonging to a particular behavior aggregate and apply the appropriate behavior for that aggregate. In other words, the core router only has to determine the behavior aggregate that was previously assigned by the edge router.
Resources are typically allocated statically for each class. For example, assume that the gold class is assigned a bandwidth usage of 10 Mbps, and the silver class is assigned a bandwidth usage of 5 Mbps. The problem with this scheme is that the actual service that a particular flow sees depends not only on the assigned AF class, but also on the current total load that the AF class is observing. In the above described example, the gold class may have 10 streams that together are consuming 10 Mbps, and the silver class may have 1 stream that is by itself consuming 5 Mbps. Thus, the streams in the gold class each get 1 Mbps of bandwidth, while the silver stream gets 5 Mbps. Of course, each stream of the gold class should ideally be allocated more bandwidth than each stream of the silver class. However, due to the heavy load on the gold class, the streams of the gold class are temporarily short changed.
In view of the foregoing, there is a need for improved methods and apparatuses for providing differentiated services. Specifically, there is a need to provide actual load information for each class so that resources may be more efficiently and reliably allocated to each class.